We have devised procedures for the isolation, purification, dissolution and characterization of four of the membrane systems of the facultative photosynthetic bacterium Rhodopseudomonas sphaeroides. Purification, identification and quantitation of individual membrane proteins and phospholipids are in progress. Freeze-fracture electronmicroscopic studies of the pigmented membrane system are in progress and results will be correlated with the structual studies pertaining to membrane biosynthesis and physical characterization. Physical studies employing the fluorescent probe, alpha-parinaric acid, are in progress and will be used in conjuction with synchronous synthesis of ICM-phospholipid. Experiments relevant to phospholipid metabolism and the exchange of phospholipids are presently underway, particularly purification of the phospholipid exchange protein(s). Density transfer experiments together with intrinsic density measurements have provided a model for the understanding of pigmented membrane biosynthesis and will be continued and supplemented. These studies, coupled with the use of macromolecular mutants, and in vivo kinetic experiments should provide us with a sound experimental basis for understanding the development, synthesis and regulation of pigmented membrane formation. Lastly, we have employed techniques, developed in this laboratory, to clone R. sphaeroides DNA in E. coli. The specific DNA regions being screened are for those involved in ICM-protein synthesis. Furthermore, we will continue our experiments on liposome-mediated plasmid DNA transfer.